1. Field of the Invention
This invention relates generally to a modular assembly for packaging and cooling battery cells of a lithium battery and, more particularly, to a modular assembly for packaging and cooling battery cells of a lithium battery, where the assembly includes a plurality of plate carriers to which the pouch cells are mounted and a plurality of U-shaped members to which the plate carriers are mounted and through which a cooling fluid flows.
2. Discussion of the Related Art
Generally, a lithium battery will include one or more interconnected lithium cells with each cell usually being separately sealed. For certain applications, such as a variety of vehicle applications, including fuel cell vehicles, hybrid vehicles, and electric vehicles, a hundred or more cells may be connected in series to provide the power needed.
According to the kind of electrolyte used, lithium secondary batteries are classified as lithium ion batteries, which use a liquid electrolyte, and lithium polymer batteries, which use a polymer electrolyte. Lithium secondary batteries can be manufactured in various shapes. Representative shapes of lithium secondary batteries are a cylinder and a prism, which are quite common. More recently, a flexible pouch-type lithium polymer battery has been attracting attention because of its changeable shape, excellent safety, and lightweight structure.
The electrolyte of a lithium battery can be a solid polymer bearing a dissociable lithium salt, but frequently the electrolyte is a liquid in which a lithium salt has been dissolved. The liquid commonly impregnates a porous polymer separator laminate which can be multilayered, or in some instances the porous separator is itself a lithium salt containing polymer laminate. The liquid in which the lithium salt is dissolved can be ethylene carbonate, propylene carbonate or other alkyl radical bearing carbonates, or a similar organic compound, which has a boiling point above 50° C. and relatively low vapor pressure at room temperature. The electrolyte layer is located between the electrodes. Laminar lithium batteries are constructed of at least three layers, and the layered construction together with current carriers, are wrapped in a pliable polymer laminate container which thus forms a pouch.
One manner of sealing a lithium cell is to encase the cell in a plastic laminate covered foil pouch, where the foil is usually aluminum. The cell has a positive electrode, a negative electrode, an electrolyte and positive and negative current collectors or leads enclosed in a foil pouch. The current collectors provide electrical communication between the positive and negative electrodes and an outside of the pouch.
The foil pouch has an inner face coated with a polymer laminate to both protect the foil from the electrolyte and to prevent short circuiting between the positive electrode and negative electrode and the leads. Preferably the foil pouch is also coated on its outer face with a polymer laminate.
For obvious reasons lithium batteries are sensitive to moisture and atmospheric corrosion. Therefore, the polymer pouches are sealed, usually by applying pressure and heat around the edges of the polymer laminate. Heat sealing a polymer laminate to another polymer laminate usually provides a satisfactory bond; however, the metallic leads or current collectors exiting in between the polymer layers may provide incomplete sealing, possibly resulting in seepage of the electrolyte liquid in spite of all efforts to achieve a fast seal.
Although sealed pouch cells have numerous advantages associated with their construction and relatively thin profile, they are more easily damaged than cells encased in a more rigid enclosure. Thus, there is a need in the art to provide mechanical stability to the pouch cells. However, such mechanical stability should be done in such a way so as to minimize the amount of space and materials required, as well as provide a cooling function for each individual pouch.